Synergistic Process And Mechanism Of Dichloromethane Removal By By Biopurification Cooperated With VUV

Air pollution has become an increasingly prominent environmental problem. While treatments of NOx and SO2pollution continue to receive adequate attention, effective control of volatile organic compounds (VOCs) emitted from petrochemical, pharmaceutical and other industrial processes is one of the important ways to improve atmospheric environment, As a competitive alternative to traditional technologies such as physical and chemical processes, biopurification technology has many advantages such as lower costs and less secondary pollution. Thus, it has been widely used in treatment of large flow, low and medium concentration, and easy biodegradable VOCs.However, the single biopurification process is not efficient for treatment of insoluble and less biodegradable compounds.In this paper, the vacuum ultraviolet (VUV) technology was used as a synergistic and reinforced pretreatment for biodegradation of dichloromethane (DCM), research on the influence factors, intermediates and kinetic analysis was conducted with the optimal conditions and degradation mechanism determined, DCM biopurification was studied with process parameters optimized and its pathway and mechanism expounded, effect of the integrated VUV and biopurification technology on efficient synergistic DCM purification as well as optimization of parameters was investigated with the synergistic and reinforcement mechanism discovered.In this research, effects of factors including EBRT, inlet concentration, reaction media etc. on DCM photodegradation were studied systematically, a photodegradation pathway was proposed by analysis of the identified intermediates, kinetic models were established to quantitatively describe the mutual relationship between inlet concentration, outlet concentration and EBRT. DCM photodegradation was achieved by the combined roles of photolysis, OH·and O3photooxidation, and the main intermediates were micromolecular aldehydes and ketones, and carboxylic acids such as formaldehyde,formic acid,acetic acid, and glyoxylic acid etc.,with greatly enhanced solubility. BOD/COD test results showed that the biodegradability of photodegradation intermediates was significantly improved, providing a basis and possibility for enhanced biodegradation efficiency.One DCM bacteria capable of degrading DCM, Pandoraea sp. LX-1(Genebank NO:JN021530, Collection No:CCTCC M2011242) was selected from the aeration tank of Hangzhou Sibao Wasterwater Treatment Plant, with the optimal culture conditions of temperature32℃, Culture medium concentration and salinity7.28and0.66%respectively. BTF and BF packed respectively with either-based polyurethane foam and nutrition slow release fillings were built for purification of DCM。The start-up of BF and BTF was finished by gas-liquid phase joint reverse inoculation within25d and22d, respectively. Stable operational experiments showed that the maximum removal load of DCM by BF and BTF were respectively23.2g·m-3·h-1and33.46g·m-3·h-1.BTF and VUV-BTF were built, and their startup was finished with21d and18d, respectively Stable operational experiments showed that with DCM inlet concentration of400-600mg·m-3, relative humidity of75～80%and the same EBRT DCM, removal efficiency by the integrated VUV-BTF system was14～22%higher than that by the single BTF system, with their maximum mineralization rate of81.56%、73.16%, respectively. In the integrated system, the transformation of DCM pollution load was mainly conducted by the VUV section while the mineralization was mainly undertaken by the BTF section. The mass and biodegradability in BTF were intensified by photodegradation, thus a synergistic purification of higher concentration DCM was made possible in the integrated system, with its removal capability higher than the combined removal capability of the single VUV and BTF processes. EPS analysis showed that the integrated UV-BTF system had a better biofilm activity than BTF, more use of trace elements, more optimal biofilm thickness and more diversified biomass population. Engineering application analysis indicated that the integrated UV-BTF technology had greater adaptability to unstable application conditions and thus better environmental and economic prospects.